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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:43:23 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:43:23 -0500 |
commit | 218934fa2ed1c702a6d3923d2aa2cc6b43c48684 (patch) | |
tree | a9ef8ac1e1b8fe4207b6d64d3841bfb8990b6fd0 /files/zh-tw/web/javascript/reference/global_objects/array/isarray/index.html | |
parent | 074785cea106179cb3305637055ab0a009ca74f2 (diff) | |
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diff --git a/files/zh-tw/web/javascript/reference/global_objects/array/isarray/index.html b/files/zh-tw/web/javascript/reference/global_objects/array/isarray/index.html new file mode 100644 index 0000000000..f610cd1f54 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/array/isarray/index.html @@ -0,0 +1,134 @@ +--- +title: Array.isArray() +slug: Web/JavaScript/Reference/Global_Objects/Array/isArray +tags: + - Array + - ECMAScript5 + - JavaScript + - Method + - Reference + - polyfill + - 方法 + - 陣列 +translation_of: Web/JavaScript/Reference/Global_Objects/Array/isArray +--- +<div>{{JSRef}}</div> + +<p><code><strong>Array.isArray()</strong></code> 函式會檢查傳入的值是否為一個 {{jsxref("Array")}}。</p> + +<pre class="brush: js">Array.isArray([1, 2, 3]); // true +Array.isArray({foo: 123}); // false +Array.isArray('foobar'); // false +Array.isArray(undefined); // false +</pre> + +<h2 id="Syntax" name="Syntax">語法</h2> + +<pre class="syntaxbox">Array.isArray(<var>obj</var>)</pre> + +<h3 id="Parameters" name="Parameters">參數</h3> + +<dl> + <dt><code>obj</code></dt> + <dd>要檢查的物件。</dd> +</dl> + +<h3 id="回傳值">回傳值</h3> + +<p>若物件為 {{jsxref("Array")}} 回傳 <code>true</code>;否則回傳 <code>false</code>。</p> + +<h2 id="Description" name="Description">描述</h2> + +<p>檢查傳入的物件是否為陣列({{jsxref("Array")}}),如果是便回傳 <code>true</code>,否則回傳 <code>false</code>。</p> + +<p>更多細節請參考 <a href="http://web.mit.edu/jwalden/www/isArray.html">“Determining with absolute accuracy whether or not a JavaScript object is an array”</a>。</p> + +<h2 id="Examples" name="Examples">範例</h2> + +<pre class="brush: js">// 下方都回傳 true +Array.isArray([]); +Array.isArray([1]); +Array.isArray(new Array()); +Array.isArray(new Array('a', 'b', 'c', 'd')); +Array.isArray(new Array(3)); +// 小細節:Array.prototype 本身是陣列: +Array.isArray(Array.prototype); + +// 下方都回傳 false +Array.isArray(); +Array.isArray({}); +Array.isArray(null); +Array.isArray(undefined); +Array.isArray(17); +Array.isArray('Array'); +Array.isArray(true); +Array.isArray(false); +Array.isArray({ __proto__: Array.prototype }); +</pre> + +<h3 id="instanceof_vs_isArray"><code>instanceof</code> vs <code>isArray</code></h3> + +<p>當檢查 <code>Array</code> 實例時,<code>Array.isArray</code> 相較於 <code>instanceof</code> 更加推薦,因為它可以穿透 <code>iframes</code>。</p> + +<pre class="brush: js">var iframe = document.createElement('iframe'); +document.body.appendChild(iframe); +xArray = window.frames[window.frames.length-1].Array; +var arr = new xArray(1,2,3); // [1,2,3] + +// 正確地檢查陣列型態 +Array.isArray(arr); // true +// 有害地,因為它不能在 iframes 之間正常運作 +arr instanceof Array; // false +</pre> + +<h2 id="Polyfill">Polyfill</h2> + +<p>如果 <code>Array.isArray()</code> 不存在於您的環境,在其他程式碼前執行下列程式碼可建置 <code>Array.isArray()</code>。</p> + +<pre class="brush: js">if (!Array.isArray) { + Array.isArray = function(arg) { + return Object.prototype.toString.call(arg) === '[object Array]'; + }; +} +</pre> + +<h2 id="Specifications" name="Specifications">規範</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('ES5.1', '#sec-15.4.3.2', 'Array.isArray')}}</td> + <td>{{Spec2('ES5.1')}}</td> + <td>Initial definition. Implemented in JavaScript 1.8.5.</td> + </tr> + <tr> + <td>{{SpecName('ES6', '#sec-array.isarray', 'Array.isArray')}}</td> + <td>{{Spec2('ES6')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-array.isarray', 'Array.isArray')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="Browser_compatibility" name="Browser_compatibility">瀏覽器相容性</h2> + +<div> + + +<p>{{Compat("javascript.builtins.Array.isArray")}}</p> +</div> + +<h2 id="See_also" name="See_also">參見</h2> + +<ul> + <li>{{jsxref("Array")}}</li> +</ul> |